Technical Field
The present disclosure relates generally to hydrodynamic face seals.
Description of the Related Art
Spiral groove lift-off seals (also known as hydrodynamic seals or hydrodynamic face seals) have been used successfully for many years in the industrial gas compressor industry.
Generally, the seal assembly involves a system fluid pressure (e.g., gas density). The high fluid pressure may be located on either an inside diameter of a seal assembly or the outside diameter of a seal assembly. The seal assemblies may comprise two rings where a face of each ring is adjacent to one another. A first ring may be a stationary member, also known as a seal ring, and may be movable only in an axial direction. A second ring may be a rotational member, also known as a mating ring or rotor, which may rotate about an axis that is generally shared by the two components. The second ring may contain a plurality of grooves on the face adjacent to the first ring. The grooves, which may be spiral in shape, may be grooved toward a low pressure side of the second ring. The grooves may have a dam section where the groove ends. A sealing, effect around the dead ended grooves can provide a compression of a working fluid, such as gas, resulting in a pressure increase in the groove region. The increase in pressure can cause the faces to separate slightly, which can allow the pressured fluid, such as air, to escape the grooves. A steady state force balance between opening and closing forces may be generally achieved at some determinable face separation gap. The seal may operate in a non-contact mode above some threshold rotational speed.
However, when employing conventional hydrodynamic groove technology for the purpose of producing a film riding seal (e.g., non-contacting) in or under certain conditions, such as the outside environment of an aircraft at cruising altitude, the ability for a sufficient amount of fluid to enter the hydrodynamic grooves may be diminished due to a lower speed, lower density, and/or a rarefaction of the fluid. The resulting hydrodynamic fluid film between the rotating mating ring and the stationary seal ring can be significantly reduced. Thin hydrodynamic fluid films may be less stable than desired and may result in higher heat generation due, for example, to intermittent contact from transient conditions and high vicious shear of the fluid.
Among other things, the present disclosure addresses one or more of the aforementioned challenges.